Vehicle windshield cleaning system

ABSTRACT

Apparatus and method for providing a heated cleaning fluid to a vehicle surface. The apparatus has an inlet port for receiving an amount of fluid; an outlet port for dispensing an amount of heated fluid two glow plug heating elements and a control for activating or energizing the glow plugs to heat fluid within a reservoir.

RELATE BACK

The present application claims priority from provisional applicationSer. No. 60/952,036 and is a continuation in part of co-pendingapplication Ser. No. 11/341,116 filed Jan. 27, 2006 which is acontinuation in part of application Ser. No. 10/894,266, filed Jul. 19,2004 (claiming priority from provisional application 60/551,571), whichis a continuation in part of application Ser. No. 10/653,827 filed onSep. 3, 2003, now U.S. Pat. No. 6,902,118 which is a continuation inpart of U.S. Ser. No. 10/269,647 filed Oct. 11, 2002 (claiming priorityfrom U.S. provisional application 60/415,552), now U.S. Pat. No.6,851,624, all of which are incorporated herein by reference and fromwhich priority is claimed.

FIELD OF THE INVENTION

The present invention concerns a windshield cleaning system, and moreparticularly to a windshield cleaning system that heats cleaning fluidapplied to the windshield.

BACKGROUND ART

U.S. Pat. No. 6,364,010 entitled “Device to Provide Heated Washer Fluid”to Richman et al. concerns an apparatus and method for improving thecleaning and deicing effectiveness of a washer fluid in a motor vehiclebefore spraying it against a windshield, headlamps, etc, and utilizesthe heat from the engine coolant to elevate the temperature of thewasher fluid. U.S. Pat. Nos. 5,957,384 and 6,032,324 also concernde-icing of a windshield.

SUMMARY OF THE INVENTION

The invention concerns apparatus and method for providing a large amountof heated cleaning fluid to a vehicle surface. An exemplary system hasan inlet port for receiving an amount of fluid; an outlet port fordispensing an amount of heated fluid; a heating element that heats upfluid passing from the inlet to the outlet; and a control circuit forenergizing the heating element with a voltage to heat the fluid passingfrom the inlet to the outlet.

In one exemplary embodiment, the system provides heated cleaning fluidto a vehicle surface and includes structure defining an inlet port forreceiving an amount of fluid, an outlet port in fluid communication witha reservoir for dispensing an amount of heated fluid.

These and other objects advantages and features of the invention willbecome better understood from the following detailed description of oneexemplary embodiment of the present invention which is described inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram schematic of a representative system for usewith the present invention;

FIG. 2 is an alternate block diagram schematic of a representativesystem for use with the present invention;

FIG. 3 is a schematic diagram of a drive circuit coupled to a fluidheating element that forms part of the FIG. 2 system;

FIGS. 4-7 are schematic depictions of control circuits for use with awasher control system constructed according to an alternative embodimentof the present invention;

FIG. 8 is a perspective view of a heating assembly coupled to a fluidpump;

FIG. 9 is a plan view of an exemplary heating canister constructed inaccordance with the invention; and

FIG. 10 is a view as seen from the line 10-10 in FIG. 9;

FIGS. 11, 12, and 13 depict an alternate embodiment of a fluid heatingsystem;

FIGS. 14 and 15 illustrate operation of a check valve for use with theinvention; and

FIGS. 16 and 17 are schematic diagrams of a representative system foruse with the present invention as shown FIGS. 9 and 10.

EXEMPLARY EMBODIMENT FOR PRACTICING THE INVENTION

The drawings depict embodiments of the present invention that concern awasher control system 10 for use with a vehicle. In the disclosedexemplary embodiments of the invention, the control system 10 is used inconjunction with a windshield washer apparatus. The control system 10includes a control circuit 14 that includes an electronic output drivesignal circuit 20 and an input signal interpretation or conditioningcircuit 16.

The input signal interpretation circuit 16 electronically interfaceswith at least one temperature sensor 18. In one embodiment of theinvention, the temperature sensor provides signals related to thetemperature of washer fluid supplied to windshield spray nozzles on thevehicle. In one embodiment of the invention, the control system alsoincludes an electronic output circuit that drives an output powercontrol for at least one heating element that heats the windshieldwasher fluid. One exemplary control system could have both “high side”and “low side” type drives working together as illustrated in FIG. 2. Analternate control system is a “low side” type drive, meaning the moduleactivates and deactivates the heater element by controlling theelectrical circuit path to ground. Another alternate control systemcould have an output drive that is a “high side” type, meaning themodule activates and deactivates the heater element by controlling theelectrical circuit path to a power source. In accordance with anotheralternate control system, an electrical interface coupled to a vehicularcommunication bus allows the control system to be controlled by vehiclecommunications and makes data available to the vehicle for operation anddiagnostics of the control system.

The control circuit 14 includes a programmable controller ormicroprocessor 14 a that implements control algorithms for washer heatercontrol output functions in response to vehicle input signals. As seenin the functional schematic of FIG. 1, the control system 10 includes anelectronic output 12 from the control circuit 14 for providingcontrolled current to the heating element 30. Heating element 30 may becomposed of a single heating element or multiple heating elements. Byselecting heater current draw and power rating the heating time andtotal system current draw can be modified over a wide range of operatingparameters based on individual vehicle requirements, ie. electricalpower available. The control circuit 14 also includes an input signalinterpretation circuit 16, or interface, to monitor input signals from,as one example, the temperature sensor 18. The temperature sensor 18provides signals that allow for control of the amount of power deliveredto the heating element 30. The controller monitors inputs from a vehiclebattery 40 and vehicle ignition 42. It is understood that a separateignition input 42 may not be required if all power is obtained from thebattery input 40. In accordance with another alternate embodiment asillustrated in the functional schematic of FIG. 2, the controller alsomonitors a user input and drives a vehicle washer fluid pump 45 a (FIG.8) having a pump motor.

In one exemplary embodiment, the electronic output circuit 20 controlspower coupled to a heater element 30 (FIG. 1) that includes two glowplugs 30 a, 30 b (FIG. 10), or other heating element equivalents such asnichrome wire, ceramic heaters, or any metallic or non-metallic typeheater mounted in thermal contact with a heat exchanger 80 as shown inFIGS. 9 and 10. Fluid is routed past the heat exchanger 80 in thermalcontact with these elements by routing fluid into an inlet 32 andforcing the fluid out an outlet 34 having a check valve to prevent fluidleaving the outlet 34 from re-entering a fluid reservoir 103. Thecheckvalve could be positioned on the inlet 32. The inlet receiveswasher fluid from a fluid reservoir 35 (FIG. 8) of a motor vehicle andthe outlet 34 delivers heated washer fluid to nozzles 37 (FIG. 8)mounted to the vehicle which direct the washer fluid against the vehiclesurface, typically a windshield, headlamps etc. In the exemplaryembodiment the heating elements 30 a, 30 b are glow plugs. FIGS. 9 and10 depict an exemplary embodiment of a housing 41 that defines a fluidreservoir 103 that surrounds the heat sinks. The housing 41 isconstructed from plastic, or other material with favorable thermalcharacteristics.

The programmable controller 14 (FIG. 1) constructed in accordance withthe exemplary embodiment of the invention implements control algorithmsfor washer heater control output functions in response to vehicle inputsignals. As washer fluid temperature changes due to ambient temperaturechanges, battery voltage changes, and the like, the duration of appliedheat is increased or decreased in order to maintain a washer fluid at ornear a target temperature. Control of the heating may also includeredundant failsafe mechanisms such as a thermal fuse 524 (FIG. 9).

Controller Schematics

The block diagram shown in FIG. 1 and the more detailed schematic ofFIG. 4 depict operation of a control system 10 having externalelectrical connections, which include Battery 40, Ground 44, andIgnition 42. The system block diagram 111 shown in FIG. 2 shows furtherexternal electrical connections including a user operated Clean Switch113 and an output 115 to drive a vehicle washer pump motor. The Batteryinput connection 40 provides the voltage supply needed by the controlsystem 10. This connection allows the high current flow required by theheating element. The Ground connection 44 provides the current returnpath to the battery negative terminal. This ground connection allows thehigh current flow required by the heating element plus the requirementof the control system 10. An Ignition input 42 provides power to thecontroller. It is understood that separate ignition input 42 may not berequired if all power is obtained from battery input 40. The batteryvoltage is monitored by the controller 14 to determine if there issufficient voltage present to allow the control system to operate.

The input 102 from the temperature sensor 18 in physical contact withthe heat exchanger 80 is directly related to washer fluid temperature.Washer fluid temperature is monitored by using a temperature sensor suchas a thermistor, RTD, or the like. The washer fluid is monitorednon-invasively by attaching the temperature sensor to the heater.Alternatively, the fluid temperature could be monitored invasively byplacing a temperature sensor directly into the fluid through a threadedfitting or other suitable attachment method.

Operation

The controller receives a wake-up command signal from the Ignition input100 (FIG. 3). When the Ignition input is above a predetermined voltage,the controller 14 drives the heater element 30 if the following aretrue:

-   -   1. The ignition voltage is greater than a first predetermined        level and less than a second predetermined level.    -   2. The sensed Heater element temperature is less than a        predetermined level.        Cleaning the windshield with warmed fluid can be accomplished by        the following:    -   a. Application of ignition 42 will cause the unit to heat the        volume of fluid. During the heating time an indicator LED 119        flashes. Alternately, the LED could remain off until the fluid        has been heated at which time the LED will turn on either 100%        or flashing. The LED is shown as part of the clean switch 113,        but a skilled artisan could move the indicator external to the        switch.    -   b. During heating of the fluid if the clean switch 113 is        pressed, the LED will begin flashing to confirm the operator's        desire to use smart mode. If heating has already completed and        the indicator lamp is illuminated (not flashing), momentarily        activating the clean switch 113, initiates a smart mode        consisting of the energization of a washer pump and wiper motor.        During heating    -   c. Output 115 activates the washer pump 117 to dispense fluid on        the windshield. In the embodiment shown in FIG. 4, an external        controller 123 activates a wiper motor 121 in response to a        signal from the washer switch 113. One skilled in the art could        have the same controller 14 activate the wiper motor 121 and the        washer pump 117.    -   d. Hot fluid will be sprayed on the windshield and the        windshield wipers will cycle automatically, when the hot fluid        reduces to a predetermined temperature or time, output 115        deactivates, thus completing the smart mode and washer        spray/wiper cycling will halt. Momentarily pressing clean switch        113 during the smart mode will cancel the operation. The        cleaning switch can be configured to heat fluid to a        predetermined temperature (or time) and dispense and reheat and        dispense fluid multiple times.    -   2. With ignition 42 applied and when indicator 119 is        illuminated (not flashing) indicating warm fluid is available,        the activation of the existing vehicle wash switch will dispense        fluid for as long as the switch is closed for on-demand        cleaning.    -   3. The activation of the existing vehicle wash switch will        dispense fluid for as long as the switch is closed for on-demand        cleaning regardless of fluid temperature.

An output driver 20 depicted in FIG. 1 and FIG. 2 applies power to theheater after starting the heating cycle. The output driver will thenbegin applying power to the heater to maintain the temperature of thefluid. A fuse 55 is located between the battery connection and theheater element external to the housing 50 in the illustrated embodimentas shown in FIG. 8. An alternative embodiment could have the fuse 55internal to the housing as shown in FIG. 1. In the exemplary embodimentof the invention, the desired heater temperature is predetermined to bein a range between 120 and 150 degrees Fahrenheit. Placing thetemperature sensor 18 in physical contact with the heating element andmaintaining the heater temperature at a temperature at or below 150degrees Fahrenheit prevents the heating element from heating thecleaning fluid to an undesirable temperature, such as boiling. Thishelps prevent the formation of mineral deposits that could potentiallyclog the nozzle 37 (FIG. 8). As depicted in FIG. 9 if the temperaturesensor 18 is not mounted directly on the heating element, but is ratherlocated in the fluid reservoir 103, only an approximate, latentmeasurement of the heating element temperature is sensed. This wouldallow the heat exchanger 80 to heat to a temperature that is hotter thanthe desired fluid temperature in reservoir 103 and potentially cause theformation of nozzle clogging mineral deposits. The output driver 20(FIGS. 1, 2) will remain active as long as the ignition voltage is abovea predetermined voltage and the heater temperature is below the desiredheater temperature as determined by the temperature sensor 18. When theignition 42 is turned off, the controller is deactivated.

FIG. 3 depicts one implementation of the output circuit 20. A heaterconnection 60 is shown in the upper right hand portion of the FIG. 3depiction. This connection is grounded by means of initiating conductionof two power Field Effect Transistors (FET) 110, 112 which provide acurrent path to ground from the heater connection 60 to the groundconnection 44 through a pair of reverse polarity protection FETtransistors 114, 116. The two transistors 110, 112 are turned on orrendered conductive by means of a pre-drive transistor 120 that iscoupled to an output 122 from the microprocessor controller 14 a (FIG.1). First consider a high signal from the controller 14 a at this output122. This turns on transistor 120 that pulls an input 124 of a totempole transistor combination 126 low. This signal turns on a lower of thetwo transistors of the totem pole combination to send an activationsignal that turns off the two FETs 110, 112.

When the controller provides a low output from the controller 14 a atthe output 122, the transistor 120 turns off and pulls an input 124 to atotem pole transistor combination 126 high. This signal turns on anuppermost of the two transistors of the totem pole combination to sendan activation signal that turns on the two FETs 110, 112.

In the illustrated embodiment, a comparator 140 monitors current throughthe transistors 114, 116 (and by inference the transistors 110, 112) anddeactivates the transistors in the event too high a current is sensed. Afive volt signal that is supplied at an input 142 from a power supply(FIG. 1) provides a reference input 144 to the comparator 140. When thenon-reference input exceeds the reference input due to a rise in thecurrent through the transistors 110, 112 (and associated rise in thevoltage across the transistors 114, 116) the output 146 of thecomparator goes low and removes the input from the gate of the FETs 110,112 that causes them to conduct. This low signal at the output 146 isalso coupled to the controller so that the controller can respond to theover current condition.

In accordance with the exemplary embodiment of the invention athermistor temperature sensor 18 is also coupled to the controller. Asignal at a junction between the temperature sensor 18 and a resistorcoupled to the five volt input 142 generates a signal at an input 150related to the temperature of the heater element 30 (FIG. 1).

Referring to FIG. 9, in one embodiment, the control circuit 14 ismounted to a printed circuit board 92 supported by a housing 41. As seenin FIG. 3, a connector 60 is a bent metallic member that attaches to theheating element 30 in the vicinity of the printed circuit board 92 andis in physical contact with the circuit components on the printedcircuit board. The connector 60 thereby not only acts as a path toground for current passing through the heating element 30 but acts as aheat sink that transmits heat away from the printed circuit board.

The exemplary control circuit includes a microcontroller as shown inFIG. 1 running at an internal clock frequency of 4.0 Megahertz. In theexemplary embodiment, the microcontroller 14 a selectively energizes theheating element 30 based on a voltage applied to the control circuit.This voltage may be the battery voltage 40 and/or the ignition voltage42. When the ignition input voltage is applied, the control circuit willpower up, come out of reset, and wait for a start delay time imposed bythe controller to allow the vehicle's electrical system to becomestable. After this start delay, the control circuit monitors theignition voltage to determine if the ignition is above a minimum enablevoltage. A temperature signal from the sensor 18 is also monitored tosee if the temperature of the fluid is below a set point temperature. Anoutput drive feedback signal is also monitored to ensure that the outputis in the correct state. If all conditions are such that the output canbe enabled, the output 122 (FIG. 3) to the transistor 120 is pulled low.This initiates fluid heating. Initially, the output drive is on 100% fora maximum on time or until the feedback temperature reading approaches aset point temperature. In one embodiment, a preset maximum on time isempirically derived to stay below the boiling point of the cleaningfluid. Subsequently the control will read the heating element 30temperature and make a determination if power should be reapplied. Ifthe sensed temperature is below the desired setpoint, the output will bere-enabled at a variable duty cycle so that the heating element 30 isheated to the setpoint goal temperature as quickly as possible withoutexceeding a maximum allowable overshoot temperature.

Normal operation consists of maintaining the fluid temperature at thedesired setpoint temperature by varying the duty cycle at which voltageis applied across the heating element 30. The output duty cycle changesbased on how far the sensed temperature is below the set pointtemperature.

In the event of excessive current flow through the power drive 20, theoutput 12 will automatically be disabled. In this event the signal atthe output 146 from the comparator 140 (FIG. 3) will go low. When thisoccurs the controller 14 a disables the output to the transistor 120 fora period of time equal to an output retry rate programmed into thecontroller 14 a. If the fault condition is removed, normal operation ofthe temperature set point control is re-instituted. An alternateembodiment could have the current sense capability implemented by thecomparator 140 omitted.

In the event the operating voltage from the battery (and ignition) istoo high or too low (≧16.5 and ≦8 volts respectively) the controller 14a disables the output 12 for a timeout period. After the timeout period,if voltage conditions are within normal parameters, the controller againenables the output. It is understood that the operating voltage rangecan be set to whatever voltages are required for a particularapplication. The exemplary system also incorporates a soft turn-on andturn-off of the heating element. The soft turn-on and turn-off isaccomplished by a slow ramp up or down of the output 20 that drives theheating element. The ramping of power reduces the amount of flickeringthat can be observed from the vehicle headlights. It is recognized thatthe FET drivers could be run linearly to accomplish the soft turn-on andturn-off of the heating element. It is also recognized that the FETdrivers could be run linearly to regulate the temperature of the heatingelement. It is further recognized that if the FET drivers are runlinearly they will produce quantities of heat that will aid in theheating of fluid in the system.

FIGS. 5 and 6 illustrate an embodiment of a washer control system 10that is different from that described previously due to the replacementof control circuit 14 with a thermal fuse device 524 and a bi-metaldevice 525. FIG. 5 is a schematic depiction of such a control circuit.The thermal fuse 524 prevents the washer control system 10 fromoverheating, while the bi-metal device 525 regulates heating duringoperation. The bi-metal device could control a relay 612 (see controlcircuit schematic of FIG. 6) that supplies power to the heating element.In addition, at least one temperature sensor could be used inconjunction with a reference to control a relay that supplies power tothe heating element.

In FIG. 7, the heater 30 is energized with battery voltage by a relay632 that is activated by ignition of the vehicle. A thermal fuse 637 isin series with the relay coil and is in proximity to the heater 30. Ifthe heater becomes too hot, the thermal fuse 637 will open and voltageis removed from the heater. The control circuit 14 shown in FIG. 1provides a digital signal to a heater energization circuit 630 shown inFIG. 7. A digital signal 635 from the controller is converted to ananalog voltage by a converter circuit 638. The converted voltage isprovided to a FET 645 as a gate voltage. The gate voltage varies betweenzero to a FET saturation voltage. The FET 645 is part of a current pathfor the heater 30 and dissipates an amount of heat that is proportionalto the driving voltage that is supplied to it. Since battery voltage ismonitored, and the resistance of the heater is known, current flowingthrough the heater can be calculated by the control circuit 14 to setand regulate the gate voltage. By controlling the relative amounts ofpower dissipated in the FET and heater, the control circuit can applyvarying amounts of current to maintain a desired fluid temperature. Bycontrolling the rate of rise and fall a soft turn an/off can beachieved.

FIGS. 9 and 10 illustrate an exemplary fluid heating assembly thatprovides a heated cleaning fluid to a vehicle surface. A plastic housing41 defines an interior reservoir 103 and including an inlet port 32 forrouting fluid into the reservoir from an external source. The housingfurther defining an outlet port 34 in fluid communication with thereservoir for dispensing an amount of heated fluid to a nozzle forspraying heated fluid from the reservoir onto a surface such as awindshield.

An aluminum heat exchanger 80 has struts 85 of a length to be supportedby the plastic housing in a position that is at least partially coveredby fluid within the reservoir 103. First and second transversely spacedgenerally circular hub segments 82 are coupled together by anintermediate bridging segment. Each hub supports multiple fins 84 thatextend outwardly from its associated hub to increase the surface area ofthe heat exchanger and promote heat transfer to the fluid in thereservoir. The heat exchanger may also be made out of other thermallyconductive materials such as copper. The heat exchanger is coated toprevent oxidation or reaction with fluids. In the preferred embodimentit is a PTFE penetrated hardcoat anodization.

First and second glow plug heater elements include first and second glowplugs 30 a, 30 b for heating fluid that passes from the inlet 32 to theoutlet port 34 through the reservoir 103 in contact with the heatexchanger 80. The glow plug heater elements axially extend into the hubsof the heat exchanger so that heat emitting surfaces of the glow plugs(NSN: 2920-01-188-3863) are bonded to interior curved surfaces of thehubs by a thermally conductive material to transmit heat to the heatexchanger. The glow plug heating elements are coupled at one end withgenerally conductive connector plates 96 for routing energizing signalsto the glow plugs.

A control circuit supported by a printed circuit board 92 supported bythe housing energizes the glow plugs with a voltage and thereby heatsfluid passing from the inlet to the outlet through the reservoir. Aplastic wall member 94 supported within the housing and has openings foraccommodating corresponding first and second glow plugs. A seal 95contacts the wall member and confines fluid to the reservoir bypreventing fluid from leaking outward from the reservoir past the wallmember. Air pockets 90 formed in the housing 41 surround the heatexchanger and provide insulation between the heat exchanger an theregion outside the housing. These pockets also serve as freezeprotection in the event water is frozen in the device. These airchambers allow the reservoir to expand with the freezing water. Foroptimal protection these chambers may be filled with a compressiblematerial to control the freeze expansion performance. The air pockets 90may be positioned to cover only a portion of the housing 41. Connectorsroute battery, ground and control signals to the control circuit mountedto the printed circuit board.

As depicted in FIGS. 14 and 15 the outlet 34 is defined by an end cap 91and flexible membrane 97 coupled to the housing 41. The end cap includesa center throughpassage 99 that allows fluid to flow out the outlet tothe nozzles. As fluid is forced through the reservoir, an elastomericmembrane 97 is forced against radially extending slots 98 which openinto a central passageway 99. Once the pressure is removed from thereservoir by deactivating the washer pump the membrane 97 moves from theposition shown in FIG. 14 to cover a narrow throughpassageway 105 toprevent fluid from flowing back into the reservoir from the nozzles.

FIGS. 12-13 show the system with a cover component 676 removed. In thisembodiment, control system 10 (FIG. 11) receives fluid through an inletport 681 that then enters into a heatsink 674. A previously describedpower FET component is electrically and mechanically attached to printedcircuit board (PCB) 675, using well known methods, and is joined withheatsink 674 by means of a threaded fastener or the like. The heatsink674 is preferably made from copper, or alloy materials such as aluminumthat are similarly effective in thermal transfer. The heatsink 674 isconfigured to contain a small volume of fluid, preferably situateddirectly opposite the flat mounting surface of a power FET, ideally forthe purpose of cooling power FET during system operation. Conversely,heat transferring from power FET 514 through the heatsink 674 serves toheat the fluid in the reservoir area, adding to the performance ofcontrol system 10.

A heatsink 674 also provides electrical connection between the PCB 675and a first heater coil 671 such as a coil that is depicted in U.S. Pat.No. 6,902,118 which is incorporated herein by reference. Fluid passesfrom heatsink 674 into first heater coil 671 through aperture 677,through temperature sensor fitting 678 and into second heater coil 672.Fluid dispenses into check valve block 680 through an entryway 679 andexits control system 10 by means of outlet port 673. A check valve block680 also provides electrical connection between PCB 675 and secondheater coil 672, and is preferably made from copper, or any alloymaterial capable of withstanding long term exposure to typical fluidsused in vehicle washer systems. The assembly as described is preferablyattached to base component 682 and enclosed in the cover 676 (FIG. 11),which are preferably molded from plastic material such as 30% glassreinforced polyester, such as that made by GE Plastics under the tradename Valox®. There are many other suitable materials available capableof withstanding the environment and conditions typical of those under avehicle engine compartment. Power is supplied to this embodiment ofcontrol system 10 by means of a connector assembly 683, while input andoutput commands are administered by means of a connector assembly 684.Similar connector assemblies are used in the FIGS. 9 and 10 embodimentof the control.

While the invention has been described with a degree of particularity,it is the intent that the invention includes all modifications andalterations from the disclosed design falling within the spirit or scopeof the appended claims.

1-10. (canceled)
 11. A method of providing a heated cleaning fluid to avehicle surface comprising: a) mounting a heater element in a heatexchanger and placing the heat exchanger into a fluid reservoir throughan inlet port for receiving an amount of fluid; b) coupling thereservoir to an outlet port in fluid communication with the reservoirfor dispensing an amount of heated fluid; d) heating fluid that passesfrom the inlet to the outlet port through said reservoir; e) energizingthe heater element with a voltage source to heat the heating element andthe fluid passing from the inlet to the outlet through the reservoir;and f) sensing the temperature of the heating element when voltage isapplied to the heater element and de-energizing the heater element ifthe temperature is too high to prevent thermal runaway.
 12. (canceled)13-18. (canceled)